Glenn GreenwaldThe partner of journalist Glenn Greenwald was detained for nine hours by authorities at London's Heathrow Airport while traveling from Berlin to his home in Rio de Janeiro, The Guardian is reporting.

Officials stopped David Miranda, a Brazilian citizen who lives with Greenwald in Rio, and questioned him under the controversial "Schedule 7" law in the U.K. Authorities can use the law — which only applies at ports, airports, and border areas and requires no reasonable cause for suspicion— to stop, question, search, and detain individuals under the country's Terrorism Act.

Miranda's trip, paid for by The Guardian newspaper, was to act as courier between Greenwald and documentary filmmaker Laura Poitras, who has been helping him investigate government surveillance. Using encrypted thumb drives, he delivered documents to Poitras, and headed back with documents from Poitras meant for Greenwald, according to The New York Times.

Although he was released without charge, authorities confiscated all of his electronics, including a laptop, memory sticks, his camera, and cell phone.

At the time the "security official" called me, David had been detained for 3 hours. The security official told me that they had the right to detain him for up to 9 hours in order to question him, at which point they could either arrest and charge him or ask a court to extend the question time. The official - who refused to give his name but would only identify himself by his number: 203654 - said David was not allowed to have a lawyer present, nor would they allow me to talk to him.

With a trove of documents about surveillance programs leaked from ex-NSA contractor Edward Snowden, Greenwald and Poitras have brought considerable embarrassment to both the U.S. and U.K. governments with revelations that the NSA and Britain's GCHQ have been spying on ordinary citizens.

As Greenwald points out, instead of being asked about terrorism, Miranda was apparently grilled over Poitras' and Greenwald's reporting on government surveillance.

London's Metropolitan Police Service released the following statement to The Times: "Holding and properly using intelligence gained from such stops is a key part of fighting crime, pursuing offenders and protecting the public."